buceriasdon

Scott, You will also see that the volume inside a high pressure burner is large for it's length. You can't run more pressure through a burner than it was designed for, hence my example of using a high pressure regulator on a low pressure gas grill. One needs volume and pressure, not just pressure alone.Don

Richard, Marsal seems to possess pretty strong deflection kung fu. The deflectors might be bent in some manner, perhaps to provide rigidity/stability and also better deflection. I have to admit, a flat 3 mm steel plate might not give you that level of even heating.

Steel + firebrick + H shaped burner should go a long way in giving you an evenly heated hearth. According this page

Aluminum anneals at 700. For you to reach a hearth of 650, the aluminum closer to the burner will most likely end up in the 800 realm, even if above steel. I would go with 6 mm steel and see where that gets you. The conductivity and thickness should go a long way in evening out the heat.

27 psi is more than enough for a 200K btu banjo burner, but, perhaps the lengths of the runs are impacting the BTUs here. I'm not really sure how they should, though. Regardless, if you can get 50, get 50.

If you do add holes, I would stick to holes of the same size, but I like Don's idea of a greater concentration of holes at the extremities. First see what it will do with 50 psi, though.

Scott are you sure you posted the right link. I couldn't find anything pertaining to even hearth heat.

I also think I may have caused some confusion interchanging the words 'deflector' and 'plate'. For clarity I've been thinking of sheet of metal to completely cover the 4'x2.5' hearth area. The bent deflectors that Marsal use would be good if the refractory bricks were joined so the heat can travel by conduction from one end to the other. Using small 9"x9" bricks makes it imperative that I even out the heat before it hits the bottom of the bricks.

The link you provided does talk about aluminium warping at fairly low temperatures so unless its bonded to steel I guess it's not going to be usable.

Hi Lenny. Yes, we have the same type here but someone has told me that the pressure is already regulated by the head that the gas bottle comes with. If I get that changed by the supplier I can get more pressure.

Richard, I meant LP for liquid propane,NG for natural gas. You didn't answer my question. Which size jet/orifice did you use, a smaller propane hole size or a larger natural gas orifice size? They are not interchangable. I have more but it seems important parts of posts are not being addressed.Don

Don. I'm using LPG (liquid petroleum gas) and the venturi jet size is also 2mm, same as the ports on the burner.

scott123

Don, I think I understand what you're saying. I'm looking at the pipe size on the burner and seeing a diameter that would allow hundreds of thousands of BTUs of gas to pass, but this isn't about the diameter of the pipe, it's about the venturi. The venturi is what dictates BTUs- at least, it does in this setting. It's not about pressure or pipe burner diameter or even about hole count, size or placement, but the venturi. Without a high BTU venturi, nothing can be done.

Is that correct, Don?

« Last Edit: August 30, 2012, 04:53:06 PM by scott123 »

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buceriasdon

Richard, The standard hole sizes for LP gas and NG orifices are as follows: LP Gas Drill Size: #72 (.0250"), Natural Gas Drill Size: #56 (.0465"), your orifice/jet size is completly wrong, 2mm?¿ that's way to big to be correct and there is no reason to continue discussing your burner until you have the proper sized jets installed. Don

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buceriasdon

This is insanity to be suggesting that Richard use a high pressure burner system as it uses much more gas than than low pressure and that's a fact. He wants an efficient low water column system. Water column is a means to measure low pressure systems, ten to eleven inches is what's required. I simply won't get on that high pressure burner train.Don

This is insanity to be suggesting that Richard use a high pressure burner system as it uses much more gas than than low pressure and that's a fact. He wants an efficient low water column system. Water column is a means to measure low pressure systems, ten to eleven inches is what's required. I simply won't get on that high pressure burner train.Don

Aw Don - I measured the orifice size with my daughters ruler. Could be 1.8mm or even 1.6mm. I was wearing my crappy classes at the time . Drill size anywhere from 46 to 52.

For the amount of pressure in the cylinders I asked another one of my handy men. He reckons about 32-35 psi. Extrapolating the tables here http://www.joppaglass.com/burner/highp_chart.html it could be about right if I'm aiming for about 150000 Btus.

10-11" water pressure equates to less than 1/2psi. Seems very low and certainly difficult to get a lot of Btus. Then again I guess the average kitchen gas cooker isn't using so much.

Anyway its a bit of a mute point because if I want the larger tanks of LP they come with that pressure regulator. I don't really want the supplier having to do something special for me otherwise the running costs will go up.

Lenny = I've mentioned that the system I will be using will have a fan attachment to deliver more air to venturi. Don't know, how much more, as I haven't bought it yet. But it should be able to bump up the Btus. It should also take care of the choking that Bob mentioned in an earlier post.

« Last Edit: August 30, 2012, 10:14:54 PM by Sqid »

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buceriasdon

Richard, You can not combine a forced air and a venturi burner system. In a venturi the vacuum created by the rush of gas out of the jet pulls air into the venturi area to be mixed. A forced air system is the exact opposite, it is the rush of air that pulls gas into the flow. The principles and execution are 180 degrees out from one another. Also could someone please show me a link to a high pressure commericial oven, I don't seem to be able to locate one on the internet.Donp.s. Richard, I went back and reread your posts and can't find a mention of using forced air until yesterday.

Also could someone please show me a link to a high pressure commericial oven, I don't seem to be able to locate one on the internet.

No idea if there is one Don. All I knew about high pressure vs low pressure a couple of months ago was that I needed a high pressure regulator if I wanted a gas bottle larger than 15Kg. When I connect the gas bottle to my oven I do turn down the regulator to a minimum flow before I light it. I then increase the flow ever so slightly to get a better flame. Could well be using 'low pressure' pressure!

buceriasdon

Richard, I find it impossible to believe you can't locate a low pressure regulator there. That's absurd, all LPG tanks are high pressure at it's outlet everywhere in the world and they all can be brought down in pressure! I've stated this before and I'll say it again, you don't want high pressure! You want to ignore my recommendations, fine, I'm tired of repeating myself over and over. Best of luck with whatever.Don

Richard, I find it impossible to believe you can't locate a low pressure regulator there. That's absurd, all LPG tanks are high pressure at it's outlet everywhere in the world and they all can be brought down in pressure! I've stated this before and I'll say it again, you don't want high pressure! You want to ignore my recommendations, fine, I'm tired of repeating myself over and over. Best of luck with whatever.Don

I shall ask again if there is a low pressure large gas bottle supplier. But I don't see it as a big deal - with a regulator I can reduce the pressure to what I need and the gas bottles are proven to work on the many ovens here.

Richard, You can not combine a forced air and a venturi burner system. In a venturi the vacuum created by the rush of gas out of the jet pulls air into the venturi area to be mixed. A forced air system is the exact opposite, it is the rush of air that pulls gas into the flow. The principles and execution are 180 degrees out from one another. Also could someone please show me a link to a high pressure commericial oven, I don't seem to be able to locate one on the internet.Donp.s. Richard, I went back and reread your posts and can't find a mention of using forced air until yesterday.

Don is 100% correct. Show me one forced air venturi (or gas meeting ambient air mixing system). None. You are going to kill yourelf and some of your workers/customers if you don't shape up. I am out.

Apparently there is a place here where I can buy the control set up. Blower, digital readout, flame sensors, alarms, thermocouples however I haven't had a chance to see it yet. It's time to see whats available! I've heard it's Chinese and comes with a hefty mark-up so I'm also talking with a Malaysian company to see what they can supply.

I need to think more about the hearth set up.Definitely need to get the heat from the burners well dispersed under the hearth as soon as possible.Options are: 1) More intricate burner2) More thermal mass (thicker steel plate)3) Better or more layers of deflectors. 4) Better stone deck (better conductivity or at least less pieces) Would be better if I could find some long 2.5' long refractory bricks less than 2.5". There may be something suitable lying around somewhere but sourcing it is not easy.

Sincere thanks for all your suggestions even if I don't immediately put them into effect.

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buceriasdon

Sorry if I come off as cross but at message 142, I did my best to say that burner was incorrect on a number of levels. Constricted flow rate, tubing size wrong, pressure can only push a gas so far due to drag inside the tube. A high pressure system is completely wrong for this application, you want a Type 1 high volume/ low pressure regulator with burners designed for that. There are only burner holes along the two outside tubes, how is that even heating? After 33 messages it appears all that was accomplished were typing lessons. So what purpose did this serve? My continued repeating you want multiple low pressure burners and manifold?? Another point, you said "Lenny = I've mentioned that the system I will be using will have a fan attachment to deliver more air to venturi." I did find that previous post BTW. I'm trying best to help you out using laymen's terms but you seem to keep changing the system willy nilly and jumping from one concept to another and leaving me to do more work at surmising what you intend to say at any given point on this thread. I've done my best to be clear and concise, at times voicing strong convictions based on facts in my replies but that door swings both ways.Regards, Don

There are only burner holes along the two outside tubes, how is that even heating?

There are 2 lines of burner holes along the outside tubes and 2 lines of burner holes across the middle H cross section. They are all burning very evenly and steadily. Think you can see this in the picture I posted at reply 149. Lighting the burner is usually a one spark affair but occasionally it helps to waft the flame along - for that reason I would not be happy to put it in a hidden area of the oven. The 2nd problem that I see is that it is not putting out 120,000 Btus - The Weber burners, although smaller, can put out about 32,000 Btus. This is due partly to the size and position of the holes, with feeder ports maybe, which are precisely placed using computerised machinery. As of this time I don't know how much I can get out of my burner until I attach a blower.

I presume you are suggesting multiple line burners as in the blogett photo that Scott posted. The more burners the better, I agree. The problem is having a reliable ignition system. I don' want a line of flames along the front of the oven in order to light the other burners running perpendicular to the face - I think that will cause uneven heating. If you have a design that you think will work I'd love to see it and maybe get it made up here or the next time I'm in Bangkok.

I'm trying best to help you out using laymen's terms but you seem to keep changing the system willy nilly and jumping from one concept to another and leaving me to do more work at surmising what you intend to say at any given point on this thread.

At the start of the thread I thought I'd made it pretty clear that I didn't know anything about how a pizza oven is put together let alone how to make a burner. The biggest breakthrough for me was when Scott gave a 3 box analogy, insulation, burners, cooking box. I'm a lot closer now to knowing what I want to build.

Again just want to let you know that I appreciate all the info you've given so far. Went to the place that sells the control systems today and they had none in stock and none on order! When I make some progress this end I will let you all know.

Richard, You can not combine a forced air and a venturi burner system. In a venturi the vacuum created by the rush of gas out of the jet pulls air into the venturi area to be mixed. A forced air system is the exact opposite, it is the rush of air that pulls gas into the flow. The principles and execution are 180 degrees out from one another. Also could someone please show me a link to a high pressure commericial oven, I don't seem to be able to locate one on the internet.Donp.s. Richard, I went back and reread your posts and can't find a mention of using forced air until yesterday.

I think I may see where the misunderstanding occured. I thought that the pipe between the ports and the orifice was called a venturi. This is not correct unless the pipe is narrowed to provide a venulli effect to pull ambient air into the flow.

I'm just referring to the pipe - if it has a specialised name or not. As Don pointed out I can't be blowing air into a pipe that has holes so I need a pipe without the inlet holes. This is what I have. Waiting to track down a control system now.

And Don the ovens and control systems I'm looking at are all run on low pressure. Don't know why I was told to get a high pressure regulator?

Looked at some other firebricks. 2"x9x9. 2.3g/cu cm. Still hoping to find some larger sizes.

Wondering if I really need stone for the roof of the oven. Maybe a 1/2" steel plate would be as or more efficient.

Richard, The standard hole sizes for LP gas and NG orifices are as follows: LP Gas Drill Size: #72 (.0250"), Natural Gas Drill Size: #56 (.0465"), your orifice/jet size is completly wrong, 2mm?¿ that's way to big to be correct and there is no reason to continue discussing your burner until you have the proper sized jets installed. Don

Been doing some reading and it seems that using whatever jets, type 1 or type 4, that I need, in the ball park, of a 3mm orifice to get 120,000 Btu. A couple of sites confirm this includinghttp://www.joppaglass.com/burner/lowp_chrt.html